Naval Undersea Warfare Center Division Newport, Code 74, 1176 Howell Street, Newport, Rhode Island 02841-1708, USA.
J Acoust Soc Am. 2013 Mar;133(3):1770-84. doi: 10.1121/1.4776177.
The presence of beaked whales in mass-strandings coincident with navy maneuvers has prompted the development of methods to detect these cryptic animals. Blainville's beaked whales, Mesoplodon densirostris, produce distinctive echolocation clicks during long foraging dives making passive acoustic detection a possibility. However, performance of passive acoustic monitoring depends upon the source level, beam pattern, and clicking behavior of the whales. In this study, clicks recorded from Digital acoustic Tags (DTags) attached to four M. densirostris were linked to simultaneous recordings from an 82-hydrophone bottom-mounted array to derive the source level and beam pattern of the clicks, as steps towards estimating their detectability. The mean estimated on-axis apparent source level for the four whales was 201 dBrms97. The mean 3 dB beamwidth and directivity index, estimated from sequences of clicks directed towards the far-field hydrophones, were 13° and 23 dB, respectively. While searching for prey, Blainville's beaked whales scan their heads horizontally at a mean rate of 3.6°/s over an angular range of some +/-10°. Thus, while the DI indicates a narrow beam, the area of ensonification over a complete foraging dive is large given the combined effects of body and head movements associated with foraging.
喙鲸在与海军演习同时发生的大规模搁浅中出现，促使人们开发了探测这些隐匿动物的方法。柏氏中喙鲸（Mesoplodon densirostris）在长时间觅食潜水时会发出独特的回声定位咔哒声，这使得被动声学探测成为可能。然而，被动声学监测的性能取决于鲸鱼的声源级、波束模式和咔哒声行为。在这项研究中，从附着在四只柏氏中喙鲸身上的数字声学标签（DTags）中记录的咔哒声与来自 82 个水听器底部安装的阵列的同时记录相关联，以得出咔哒声的声源级和波束模式，这是估计它们可探测性的步骤。四只鲸鱼的平均估计轴上明显声源级为 201 dBrms97。从指向远场水听器的咔哒声序列中估计的平均 3 dB 波束宽度和指向性指数分别为 13°和 23 dB。在寻找猎物时，柏氏中喙鲸以平均 3.6°/s 的速度水平扫描头部，角度范围约为 +/-10°。因此，虽然 DI 表示波束较窄，但考虑到与觅食相关的身体和头部运动的综合影响，在整个觅食潜水过程中，声照射区域很大。
